I consistently see a huge discrepancy from one LR to the next to the point that if I do really well on one LR I assume the next will be killer. Is this in my head?

Also - is it the case for y'all as well that the easier a RC passage is to digest, the more difficult the questions are? I can't even remember how many times I've read a RC passage and thought WTF and got -0, vs totally comprehending a passage and then getting hit with ridiculous inference questions.

Its not fully in your head but you are letting it get to you a little much. There is always one LR section that has two or three more challenging questions than the other but its not so huge a discrepancy that you should expect one to kill you and the other to be a cakewalk. More importantly it doesn't change anything as far as the approach, I certainly wouldn't waste any brain power on figuring out which is which on test day. Treat all five sections as their own test and do the best you can, its all you can do.

No two sections are equally difficult, and that difference can be non-trivial, but when I look at my student's practice tests, I notice most of the time when they miss significantly more on one section than the other, it's the second LR section. I'd attribute that to fatigue more than anything else. Try not to worry about this kind of thing, as benito suggested, just treat each section as a self-contained unit.

I always felt this way, but eventually I got to the point where it was all the same to me. But early on definitely. I think what it is, is that one section will have more question types that you're not that good at and may be a bit denser. The better you get at everything the less it matters.